Distance-measuring device



Dec. 8,1925 1.564.769

I I O. EPPENSTEIN DISTANCE MEASURING DEVICE Filed May 22. 1924 g e Sheets- S h eet 1 I? ,1

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' I am/vwvtohz' Dec. 8, 1925- 0. EPPENSTEINI DISTANCE MEASURING DEVICE F'iled May 22, 1924 6 Sheets-Sheet 6 U Y I c't- I E N c g Patented Dec. 8 19 25. I UNITED STATES PATENT. o FIcE.

or'ronrrnnsrnm, or JENA, GEBMANY, nssrenon TO rm! or cm mass, or ms,

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nrsrmcn-nmsuame DEVICE.

Application filed Ka 22, 1924. Serial n. 115,229.

To all whom it may concern:

Be it known that I, O'r'ro 'Errnnsram, a, citizen of Germany, and residing at Jena,

- Germany, have invented a new and useful Distance-Measuring Device (for which I have filed an application in Germany, May

' 31, 1923), of which the following is a specification.

The present invention deals with the task of testing uniocular telemeters, having the base-line within the instrument in a simple manner without the aid of a special correct ing lathe with respect to their state of correction and of correcting the same, if necessary. Bythe patent specification 939,366 it has become known to solve this task by, disposing a correcting mark in the ocular image-plane and by transmitting the -rays, which emanate from this mark and traverse'the one half of the telemeter in the reversed path of rays, by means of correcting reflector systems disposed in front to the other half in order to eventually reunite these rays in the ocular image-plane to an image of the correcting mark. In the examples of the said patent specificationthe correcting reflector systemsare disposed behind the entrance reflector systems; of course, it does not change the nature of the subject if the reflector systems to be disposed in front for the'purpose of correction befixed before the entrancereflecELsystems-cf theytelemeter with a view to embracing the whole system by meansof the correcting method. \Vith such arrangements one imparts to the correcting reflector systems an invariable angle of deflection of such a size that with acorreot adjustment of all parts of the telemeter to' a definite distance the image of the mark coincides with the mark itself. As a rule,-one chooses as-a whole angle of deflection of the correctin reflector systems 180, so that the proper overlapping position of the mark and the image must be existent if the telemeter be adjusted to an infinitely distant obiect.

This correcting arrangement has the drawback that the correcting mark in the ocular image-plane isvisible in the field of View which is under certain conditions objectionable. According to the present invention it is possible to avoid these drawbacks and at the same time. attain double the accuracy for the correction byusing as a correcting mark the real image of a mark disposedoutside the ocular image-plane and imaged in the reversed ath of rays into the ocular imageplane.

mark now replacing the correcting mark.

intersects the boundary line in the field of view in order that the ravs producing the image in both parts of the field of view on their path over the two halves of the telemeter are also reunited in the ocular imageplane to two partial images of the mark which may be brought into coincidence with each other. The said double accuracy is broughtabout by the fact that the rays, produced by the two partial images of the mark. traverse in opposite direction; the same optical members and that consequently the relative displacement of the image. on the state of correction of the telemeter having been impaired, is twice as large as the displacement between a physical correcting mark and its image. f

The imaging of the mark in the ocular hereby both the mark and its real image are invisible to an observer looking image-plane may .be realized in adiflerent from a laterally disposed correcting mark.

into the-axial direction. For the imaging proper a suitable imaging system is requisite. If the reflector be disposed on the outslde of theocular, the latter forms itself the imaging system or part thereof. The semitransparent reflector may also be replaced by a reflector which only covers a part of the cross section of the rays and which may besilvered semi-transparent or opaque.

"-drawback arising with all such arrangements consists in the great loss of light which is'connected withthe insertion ofa semi-transparent reflector or with the reduction of the cross section of the rays and by v which the luminosity of the image. presented to the eye is reduced at best to about one half. A particularly suitable arrangement exempt from this drawback is attained by imaging the mark into the ocular imageplane on the path of the so-called lost rays, 1. e. those rays-which are prevented from ingltraversed the two halves 0 entering the ocular by the separating prism system. As Zhese rays are besides not used forthe measurement, the whole cross section traversed by these rays may be used for imaging the correcting mark. In this.

manner one attains for the correction the same lummoslty as for the measurement without impairing in any way the passage 7 rating prism system into the eye of the observer 1n order to render visible the aris-' ing partial images of the mark. If with a telemeter construction this possibility does not readily exist because the two correcting ray pencils would strike such a part each of the separating prism system which prevents them-from entering the eye of the observer, the free passage may be attained by transmitting at any one time the correcting ray pencils by means of deflection from their direction or by the introduction of an additional inversion of the image within the area of the paths of rays not required for distance measuring to the other part of the 4 separating prism system which admits of the 'free passage of the ragls thlrough thg e tie partia eye and thus renders visi images of the mark. If, however, the correctlng ray pencils are entirely or partly prevented from entering-the eye by an opaque reflector which is inserted into the path of rays and which, whilst concealing a part of the cross section of the rays serves for imaging the mark into the ocular imageplane, and if therefore the image of the corr'ecting mark would be visible onlypartly or not at all, it is possible to render the partial images of the mark visible in a simple way by the introduction of an additional parallel displacement.

With a view .to attaining visible partial images of the invisible correcting mark it is unnecessary that both halves of the telemeter are traversed by the correcting ray pencils which are coordinate to the two partial images of the mark. It isalso possible to cause each of the two pencils to traverse twice to advantage only one each. of the two halves inopposite direction. By inserting, for instance, within the area of the path of rays a plane surface reflecting on both sides and perpendicular to the optical axis of the correctin system, the direction of the ray of each 0 the two partial pencils is inverted and eachvof them traverses the path already.

covered in opposite direction, whereby the reflecting surface causes the said additional inversion of the image. Also in thiscase the relative displacement of the image on the state of correction of the telemeter vase-1,709

ingJ been impaired, becomes aslarge as if 0th halves of the telemeter be traversed by each correcting ray pencil. Thereby it is 5 the ocular image-field with the uncorrected telemeter.

Figs. 6 to 10 show a second example; Fig. 6 is a plan elevation, Fig. 7 a section on the line 77 of Fig. 6, Fig. 8 shows a detail, FigsgQ and 10 show the image-field with the corrected and uncorrected telemeter respectively. v

Figs. 11 to 15 show a third example; Fig. 11 is .a plan elevation, Fig. 12 is a section on the line 1212 of Fig. 11, Fig. 13 shows 'a. detail, Figs. 14 and 15 show the imagefield with the corrected and uncorrected telemeter respectively.

Figs. 16 to 19 show a 'fourth example; Fig. 16 is a plan elevation, Fig. 1-7 is a front elevation, Figs. 18 and 19 show the image field with the corrected and uncorrected telemeter respectively.

Figs. 20 to 23 show a fifth exam le; Fig. 20 is a plan elevation, Fig. 21 is a ront elevation, Figs. 22 and 23 show the imagefield with the corrected and uncorrected telemeter respectivcl Figs. 24. to 27 s ow a sixth example;

Fig. 24 is a plan elevation, Fig. 25 is a front and 31 show the image field with the correct- 7 ed and uncorrected telemeter respectively. Figs. 32 to 35 show an ei hth example; Fig. 32 is a plain elevation, ig. 33 is asection on the line 33-33 of Fig. 32, Figs. 34

and 35 show the image-field with the corrected and uncorrected telemeter respectively.

Figs. 36 to 39 show 'a ninth example; Fig. 36 is a plan elevation, Fig. 37 is a section on theline 37-37 of Fig. 36, Figs. 38'

and 3!.) show the image-fieldwiththe corrected and uncorrected telemeter respectively.

Figs. 40 to 43 show a tenth example:

Fig. 40 is a plan elevation in a. section, Fig.-

41 is a front elevation, partly .in section,

-' coincidence telemeter.

- edges of the separating prism s stem 0,0. A displaceable, refractive prism represents ,in such a way that t Fig. 42 is a'section on the line 42-42 of Y Fi 41, Fig. 43 shows a detail. a

e first example (Figs. 1 to 5),shows a he objective sys-. tems are formed by two. enta onal optical square-prisms fa, rovide with an imageerecting roof eac and of two objective lenses 6. The separating prism system consists of two cemented. isosceles-rectangular prisms 0 which deflect the luminous rays, emerging from the obipctives b, by 90 each s are united in the optical axisof an ocu ar consisting of a field lens d and an eye lens e. The position of the ocular ima e-plane is such as to contain the point 0 intersection of the two the principal part of the measuring device. A cubiform" prism rays between the eld lens. at and the separating prism system a, 0 consists of two isos-' celes-rectangular prisms cemented together with their by. othenusatsurfaces, the one of which" is si vered semi-transparent, and

roduces with the aid of a lens h a real image k, of a linear'mark 11 rigidly connect ed with the instrument which image intersectsthe boundary line in the ocular field of .view and serves as a 'correctin mark. Fig. 3 shows atop plan view of t e cubie form prismg as seen from the mark 73. Two correcting reflector systems, disposed in. front of the entrance apertures of the rays of both telescope systems and consisting of two pentagonal optical square-prisms l which cause together a deflection of the rays by 180, transmit the correcting ray penoils, emerging from the correcting mark is [and traversing one each of the telescope systems a, b in the-inverted path of rays, at any one time to the other telescope system. .xTheserays are eventually reunited m the ocular image-plane to an image m of the correcting mark is. The image m coincides, on "thetelemeter being adjusted to an infinitely remote object and with an undisturbed state of correction, with the image is serving as a correcting mark. and can be perceived by the eye of the observer'through the ocular d, e since the rays emanating from it are partly deflected .by the semi transparent silvered surface of the cubiform prismg in the direction of the mark '5 but partly traverse this prism unhindered.

. The correcting mark is, however, is. concealed to the eye of the observer, If the state of correction be undisturbed, the eye sees inthe two halves of the image-field separated by a line n two partial images 0 and of the correcting mark 1n colncidence 1n the posiv"Lion-shown in. Fig. 4. A disturbance of the state of correctionof the telemeter displaces these partial images, e. g. into two positions 0 and 12 represented in Fig. which are erted into the th of;

equidistant from the position of coinci-- dence in opposite. direction. The joriginal y an adjustment-of the measu g of the measuring scale .for the position of coincidence brought about anew to 'the mark infinite. T

The second constructional example (Figs. (Ho 10) shows in Fig. 6 the same coincidence telemeter in a plan elevation in which, howso ever, the diagonal surface of the'cubiform prism-g is s1 vered semi-transparent up to alf its height as is obvious plan view of this from the mark i. the prism gonly'actfing at half the height of the'cross section 0 rays a part of the.

rom the top rism in Fig.8 .as seen partial ray pencils which serve for imaging the correcting mark It would not be able to wing to the reflection in 3 get into the eye of the observer, so that the respective image points of the mark would be invisible. An additional prism system inserted into the part of the correcting paths of rays not required for distance measurment of the partial ray pencils whlch is requisite for this reason. Iticonsists of a prism g .havin I a -.parallelo am-shape'd cross section wit a pointed e ge-angle of 45 and. of a second'hniform prism which is itself com osed of two prisms g and g having asimi ar cross section and cemented with 1 Theboundary surface between q and is refiectingon'both sides. Fig. 9 shows images. of the mark 0 and p coinciding with an undisturbed state of correction of the telemeter; Fig. 10 with the partial images of the marko andv 12 with a disturbed state of correction. The'correcting "rocess is the same asthat described in the rst constructional example. A third constructional example is shown ing causes the additional parallel displaceq B are ocular image-field with the partial in Figs. 11 to 15. Thisexample entirelycorresponds to the receding one with the exment of the partial ray pencils being relaced throug th'e rism system g g", g y anjalternate para lel displacement effect.-

ception of the a ditional parallel displace,

ed with the aid of two uniform double wedges 1'. Figs. 16 to 19 show as fourth example an inversion telemeter. In this example as well as in all the following ones the imaging of a linear mark 8, disposed on the object side 1 and rigidly "connected to the apparatus, is brought about on the path of the lost rays. A lens t produces of this mark 8 in the cenlar image-plane a real image 70 which intersects the boundary line in the ocular image l square-prisms a and a field and serves as acorrecting mark. The position of the ocular image-plane is assumed to be the same as that characterized in the first constructional example. The 5 image is cannot be perceived by the eye of the observer at the ocular d, e and the ray pencil emanating from it is divided by the silvered surfaces, reflecting on both sides, of the separating prism system 0, in twor 81" tial pencils of the correcting rays w ich traverse one each of the telescope systems a, bin the reversed path of rays inthe'cross section of the lost rays The objective systenis are formed by two-penta nal optical of which the former is providedwith an image erecting roof, and

of two objective. lenses 1). Two' prisms 0 form the seliarating" prism system, two lenses d'and cthe' ocular. The measuring device is intimated bya displaceable, refractive prism f. 'With the aid of two-pentago nal optical .squarerprisrns --l the correcting mark la, in the ease of an undisturbedstate of correction of the telemetergis united to an image m, consisting oftwo coinciding; partialimageso and p,"whi clii coincides with the correcting mark, whilst'in the event of a disturbed state of correctiim it, is' imaged in two artial images 0 and p9." Figs; 18 and .19 Show 'the' ocular image-fieldior. both I oases. The correcting process ofthis fourth and all the following constructional forms 'of the "new instrument entirely "corresponds to that of the first three exampleshnless de- ,viations therefrom are particularly mentioned. 7 By using the device'shown for a. coincidence telemeter one arrives at an arrangement represented as. the fifth example in 4 Figs'; 20 to 23. As in thetelemeter shown both objective prisms a are provided with an image-erecting roof, it necessary to provide an inversion of the image in the correcting path of raysin;lorder to render visible thepartial images and p and 0 and 32 respectively to the eyej'of the observer at v the ocular d, e by which inversion the in version of the image (missing in' the prisma of the fourth example) on the second ohjective prism a is superseded again. The

correcting reflector system consiststhere- .fore of a pentagonal optical square-prism Z" and of a second penta onal optical squareprism Z which is provided with an imageinverting roof. Figs. 22 and 23 again show the ocular image-field for an undisturbed and a disturbed stateof correction of the a telemeter. 4 v

The sixth example (Figs. 2410 27) show for a uniform coincidence felemeter an additional inversion of the image by means of a Dove prism u inserted into the part of the correcting path of rays not required for distance measuring. In this casethe correcting reflector. system again consists of two prism 0 each inthe tively areonly perceived by one disturbed state of correction of one ofthe The objective systems a rejagam formed by uniform pentagonal optical square-prisms Z.

In the seventh example (Figs. 28 to 31) 7 there is brought about with the 'aid of a double wedge v, th'euremaining arrangement being the same, instead of the inversionof the image an upward and downward de- 'flection of the partial pencils of the correcting rays by a Small angle out of their direction, so that the pencils intersect in the" ocular image-field. The correcting mark, lying as a real image is of the mark a in the ocular image-field, remains invisible, whilst it is possible to render visible a part each of the partial images 0' and p and 0 and p respectively because a part each of the partial pencils of the correcting rays now falls upon such a surface of a separating prism system which deflects the rays into the optical axis of the ocular d, e. In the extreme case the wedge-angle of the double wedge 'v coultl be so chosen that the separating rism 7 system just admits of the undiminishe pas-- sage of both partial pencils.

The arrangement of the seventh example has the drawback that the two visible partial'images 0 and piand 0 and respecalf each of the exit pupi and, since in its locus lies the eye-pupil of the observer, by various parts of the eye.- .Owing to the irregularities of the eye reading errors ma arise which, however, can be obviated the use of a double-refractive rism instead of the double wedge 'v, whic prism divides an incident luminous ray in two rays having the same, opposite deflections, e. g. a Wollaston chal spar-prism. Onthis solution rests the eighth example (Figs. 32 to 35). The Wollaston prism consists of two plane-parallel plate'w havinga surface refleeting on both sides by which late. the direction of the partial pencils o the correcting rays is inverted. In the case of a telescope systems only a partial image of thecorrection mark, e. g. thepartialimage p is-disposed into the position p", WhflSt 'thB position of the partial image 0 remains the same.

The tenth example Figs. 41 to 43) relates, to an inversion te emeter, correspond ing to the fourth-example (Figs. l6 to 19).

two pentagonal optical square-prisms a and a of which the former is provided with an image-erecting roof, 1 and of two objective systems I) and 6 As a separating prism system is chosen a prism combination consisting of two isosceles-rectangular.

prisms and 0 two parallelogram-shaped prisms a and 0 having a pointed edge-angle of 45, another isosceles-rectangular prism consist of a field lens d and'an eye lens e.

At the free ends of the tubes B and B are fixed two optical square-casingsD and D. For the reception of the measuring device a p)rism casing E is inserted between B and The principal parts of 'themeasuring device form two refractive prisms f and f rotatable in opposite direction at an equal angular speed, which replace, in a known way the aforesaid'displaceable prism f and 'which can be rotated from a milled head G by means of a bevel .wheel F. The milled head G is connected with .a divided drum H which forms together with an index T fixed on the casing. E the reading device of the telemeter. On the side, opposite the ocular C, of the casing A there is provided an excavation in which is fixed on a ground glass g La perpendicular line a serving as a mark. This mark 8 is imaged into the ocular im- -age-plane by a convexo-plane lens t which is cemented to the prism 0 on the separating prism system. Two pentagonal optical square-prisms l and Z form the correcting reflector system and are disposed in a special casing 7:. In order to restore the original state ofcorrection, after its having been disturbed, serves a refractive prism 2 which is inserted-into the path of. rays and which can be displaced by a rack and pinion on a carriage guide 0 by means of a knob N fitted on the outside of the tube B The measuring ray pencil emanating from the objective reflector system a and the objective A b is reflected in the prism c in the direction of the ocular C and traverses unrefracted the prisms a" and a. As shown by hatching in Fig. 43, the upper half of the cemented surface betweenthese prisms is sil-. vered so as to reflect on both sides. plane perpendicular to the measuring ray' pencil through the lower edge of the reflecting surface, the connecting line ,of two prism edgepoints L and M, lies'in the ocular imageplane, whereby the. edge LMap ears as the boundary line of the image-fie d. Offthe measuring raypencil, emitted by the objective b ,'only the partial pencil lyingbelow the boundary line LM is transmitted recting mark.

unhindered "to the ocular, whilst the partial pencil 1 ing above this line is downwardly reflects and of notavail for the measure- -ment The measuring raypencil emerging .from the; objective reflector systemo? and the objective I) parallelly displaced in the upward direction 'in' therism at b the height of the prism i? an "reflgxzted 1n the latter in the-direction'of the ocular, whereby .the parallel displacement causes by the prism a is su erseded in the rism 0" by a like parallel isplacement in t e downward direction. It is only the partial pencil striking the silvered surface above the 1 boundar line LM which is transmitted to t e ocular,.whilst the partial pencil striking the prism surface below this line is lost for the imaging. On the path of ing from the two objective systems the mark 8 is really imaged in the ocular-image-field the lost rays of the imaging .pencils'emerg 5 through the lenst by means of the prisms c and 0. The image of the mark 8 intersects the boundar e correcting rays emitted by it traverse in two partial pencils the separating prism system and one each or the line and serves as a corobjective systems in the reversed path of rays and are transmitted during the correcting process at any one time to the other objective system by the two correcting reflector prisms Z and Z in order to be eventually united on the path of the measuring rays in the ocular image-plane to. two partial im-.

ages of the correcting mark.

With a. view to correcting the apparatus it is necessary to dispose the casing Kpara-llelly to the telemeter with the rea i set to infinite in such away thatone each of the correcting reflector systems l -and Z is inserted in front of one of the two objective reflector systems a and a. If the state of correction of the telemeter be disturbed "and if therefore the inspection at the ocular shows the image represented in Fig. 19 it is simply required to restore the coincidence ofv the two partial ima es of the mark 0 and 11 by rotating guide 0.

I claim:

the kno N and the thus caused displacement of the prism a on the carrlage 115 ng device 1. In a device for measuring distances and Y adjusting the same two telescopes, each con; taining an objective and. an entrance reflector system deflecting the optical axis a by about 90, a separating prism system comx mon to both telescopes and located behind the objectives, an ocular dis osed behind the separating prism s stem, t e separating prism system being a apted totransmitof each of the two ray pencilsystems entering the two teleseo'pesfa part to'the ocular, a

[deflecting device adapted to displace-at least one of the two images, produced by the two objectives, parallelly to the plane containing the axes of the two telescopes, a distance scale and an index coacting with this scale, one of these two parts being operatively connected with the said deflecting device, a

mark lying outside the image plane of the said ocular, an tical system disposed behind the said .0 jectives and adapted to flector system deflecting the optical axis by.- about 90, :1 se arating prism system com-- mon to both te escopes and located behind the objectives, an ocular disposed behind the separating prism system, the separating prism system being adapted to transmit of each of the two ray pencil systems entering the two telescopes a part .totheocular, a defle'ctingdevice adaptedto displace at least one of the two images, produced by the two objectives, parallelly to the plane containing the axes of the two telescopes, a distance scale and an index coacting with this scale, one of these two parts being operatively connected with the said deflecting device, a

mark lying outside the image plane of the said ocular, an optical system adapted to image the mark in this image plane on the path on which those rays emerge from the separating prism system, which are not transmitted by this system to the ocular, and a correcting reflector system, deflecting thetraversing rays by about 180 the correcting reflector system being adapted to be fixed before the telemeter and the entrance scale and an index coacting one of these two parts being operatively con- 3. Telemeter comprising two telescopes,-

each of which contalns an objective and an entrance reflector system deflecting the op-.

tical axis by about 90, a separating prism system adapted to transmit of each of the two ray pencil systems entering the two telescopes a part to the ocular, a deflecting device adapted to displace at least one of the two images, produced by the two ob-. jectives,vparallelly to the plane containing the axes of the two telescopes, a distance with this scale,

nected with the said defiectin device, a mark lying outside the image p ane of the said ocular, and an optical system disposed behind the said objectives and adapted to image the mark in this image plane.

4. Telemeter com each of which contains an objective and an entrance reflector system deflecting the op tical axis by about 90, a separating prism system adapted to. transmit. of each of the two ray pencil systems entering the two telescopes a part to the ocular, a deflecting device adapted to displace at least one of the two images, produced by the two 0bjectives, parallelly to the plane containing the axes of the two te1escopes,ya distance scale and an index coacting with this scale, one of these two parts being operatively connected with the said deflecting device, a mark lying outside the image plane of the said ocular,'and an optical system adapted to image the mark in this image plane on the path on which those rays emerge from the'separating prism system, which are not transmitted by this system tothe ocular.

OTTO EPPENSTElN.

prising two telescopes, 

